Products made from paper webs such as bath tissues, facial tissues, paper towels, industrial wipers, food service wipers, napkins, medical pads and other similar products are designed to include several important properties. For example, for most applications, the product should be highly absorbent. In addition, products often should include surface texture in order to provide, for example, a good wiping surface in the case of wiping products or a soft surface texture in products which may be used while in contact with skin. Moreover, absorbent paper products which are multi-ply laminated products should avoid delamination under conditions of use.
Methods for increasing texture at the surface of a paper product are well known in the art. One well-known method is embossing, wherein the fibers in the web are mechanically deformed under high mechanical pressure to impart kinks and microcompressions in the fibers that remain substantially permanent while the web is dry. When wetted, however, the fibers may swell and straighten as the local stresses associated with the kinks or microcompressions in the fiber relax. Thus, embossed tissue when wetted tends to lose much of the added surface texture imparted by embossing, and tends to collapse back to a relatively flat state. Similar considerations apply to the fine texture imparted to tissue by creping or microstraining, for such texture is generally due to local kinks and microcompressions in the fibers that may be relaxed when the tissue is wetted, causing the tissue to collapse toward a flatter state than it was in while dry.
Other methods are known in the art for protecting the strength of a paper web, such as when the paper web is wet. These methods, however, do little to protect the texture of the surface of the web while maintaining web strength. For example, wet strength agents may be used in tissue and other paper webs to help strengthen or protect fiber-fiber bonds of the web as it dries, but such agents do not protect additional texture imparted to the dry web by embossing, creping, microstraining, or similar processes. When an embossed web which has been treated with wet strength agents is wetted, the swelling of the fibers and/or the relaxation of stresses in the fibers tends to remove much of the embossed texture as the web returns to the topography that existed as the web initially dried when the wet strength agents became activated or cured.
Thus, there is a need for a method of converting a dry tissue web or other porous web into a structure having enhanced texture and physical properties. Moreover, there is a need for a highly textured paper product which may maintain a highly textured surface even after becoming wet.
Further, laminated products, such as laminated wiping products, for example, often experience delamination of plies during scrubbing. The use of binder fibers has been utilized in the past to join two textured webs, but this method sometimes results in weak spots where the binder fibers are scarce. Maintaining good uniformity of binder fibers between plies may be challenging, and getting good contact between the fibers and both adjacent tissue plies may also be challenging. Thus, there is a further need for a multi-ply wiping product which may maintain desired surface characteristics during use with improved contact between plies and less chance of ply delamination during use.